1. Field of the Invention
The present invention relates to implantable subcutaneous vascular access ports, for implanting beneath the skin of a patient, and for allowing vascular access for medicines to be repeatedly injected into a patient, or for drawing blood, without damaging the access site. More particularly, the present invention relates to a subcutaneous vascular access port having a uniquely-shaped internal chamber therein.
2. Description of the Background Art
A number of different implantable subcutaneous vascular access ports are known, for allowing a medical professional to repeatedly inject medicine into a patient over time. This is useful, for example, in a patient who is receiving chemotherapy treatment for cancer. Examples of some brand names for known implantable subcutaneous vascular access ports include X-Port™, Port-A-Cath®, and Vortex™. A number of these known access ports are manufactured and sold by the C. R. Bard Company of Murray Hill, N.J.
Examples of some of the known implantable subcutaneous vascular access ports include those disclosed in U.S. Pat. Nos. 4,929,236, 5,053,013, 5,092,849, 5,180,365, 5,176,641, 5,263,930, 5,743,873, 6,039,712, 6,290,677, and 6,613,013, as well as the references cited in each of these patents.
A generic example of a known prior art access port is shown in cross-section in FIGS. 1 and 2. This known port apparatus 10 includes a main port body 12 having a hollow chamber 14 formed therein. The chamber 14 is substantially cylindrical in shape, and has a substantially flat floor 16. The known access port also includes a flexible septum 18, attached to the main port body 12 and covering the hollow chamber 14. The septum 18 is formed from a resiliently deformable material such as a silicone elastomer.
The access port 10 of FIGS. 1-2 also includes a hollow outlet tube 20, attached to the main port body 12 and in fluid communication with the hollow chamber 14 thereof, via an outlet aperture 22 formed in a side wall of the main port body 12, at a location spaced above the floor 16 thereof, as shown.
Where used, one of the known implantable subcutaneous vascular access ports 10 is implanted beneath the skin of a patient's upper chest or arm, with a proximal end 21 of a catheter 24 connected to the outlet tube 20 of the device. The other, distal end of the catheter 24 is fed through the internal jugular vein, subclavian vein or arm vein, respectively, and into the central venous system. The access port 10 and the attached catheter 24 are left in place inside of the patient's body for a period of time, which may be a number of years, in some cases.
After the port apparatus 10 and attached catheter 24 are in place in the patient, a medical professional first confirms the location of the port, and also confirms that the catheter is in the venous system. Then, the appropriate skin surface is cleaned, and the medical professional is able to withdraw blood and/or inject medicine into the patient, by inserting the tip of a hypodermic needle through the overlying skin, through the septum 18 of the device, and into the chamber beneath the septum, and subsequently drawing blood or dispensing the medicine into the patient's bloodstream via the catheter.
As noted above, the access port and the attached catheter remain inside of the patient's body for a period of time. Over time, tissue may form around the port body 12, helping to embed it in place.
As time passes with the access port and catheter implanted inside the patient's body, the body's natural immune system may accumulate antibodies, myelin, fibrin and/or other materials from the blood on the tip of the catheter, which can eventually form a sheath over the catheter. This sheath can obstruct or even block fluid flow through the catheter. After such time, it often becomes necessary to follow a sequence of steps to remove the sheath, in order to clean the tip end of the catheter and resume normal operation.
When such blockage is suspected, it is normal practice to inject a dye into the access port 10. The dispersion pattern of the dye may be viewed on an X-ray of the affected area, which will enable a physician to determine whether or not the catheter tip is blocked with a sheath.
If a sheath is found to be blocking the distal end of the catheter 24, it has previously been the practice, in such an instance, to open a femoral vein and to insert a loop snare thereinto, and to advance the working end of the loop snare to the location of the sheath.
Examples of known snares usable for this purpose are described in U.S. Pat. Nos. 6,203,552 and 4,326,530, the disclosures of which are hereby incorporated by reference. The loop of the snare is then placed around the sheath-covered catheter and the loop is then manually tightened around the sheath and catheter. The sheath is then pulled off the catheter, by carefully withdrawing the loop snare while it holds the sheath.
It has been discovered that during the conventional procedure described above, a number of complications can arise.
The wire loop portion of the loop snare can be sharp, and if it is tightened too aggressively, the wire loop can cut off the tip of the catheter, which then floats uncontrolled in the bloodstream. Another complication can arise while withdrawing the loop snare, because the distal end of the catheter may break off, in response to pulling pressure, instead of releasing the sheath. The broken catheter tip then becomes a floating hazard in the bloodstream.
In either scenario discussed in the proceeding paragraph, a loose piece of the catheter tip, which has been fractured from the distal end of the catheter, becomes a foreign body which may float freely in the bloodstream, and will eventually lodge in the heart or lung, where it causes a blockage. In such a situation, further medical intervention, up to and including surgery may be necessitated, in order to retrieve the broken-off catheter tip.
Therefore, a method and apparatus is needed for reducing the risk of a tip portion of a catheter becoming loose in a patient's vascular system.
Although the known devices have some utility for their intended purposes, a need still exists in the art for an improved implantable access port, and for a method of removing a sheath from a catheter tip connected to an access port. In particular, there is a need for an improved method which will anticipate, and provide for controlled movement of a catheter fragment, in a situation where a catheter tip breaks off of a catheter during a sheath-removal procedure.